THTR operating experience

THTR is the first large pebble-bed HTR in the world. It is rated at 750 MW thermal 300 MW electrical (net). The graphite core with balltype fuel-elements and incore rods is located in a prestressed concrete reactor vessel. The plant was constructed mainly from 1971 to 1974 and again from 1982 to 1985. In between, there has been nearly a standsill due to a sequence of new licensing requirements. In September 1982 the prestressed concrete reactor vessel was pressure and leak tested. First criticality was reached in September 1983 and first current was sent out in November 1985. In September 1986 the plant achieved full power. The ample test phase was completed on February 6, 1987, when the final contractual trial run was begun. Operation has been interrupted twice for scheduled revisions of two months each. Another major shutdown (39 days) has been caused by an after Chernobyl political reaction on a minor release of aerosols (1,2 mCi or 60 % of the allowed daily discharge)